1. Field of the Invention
This invention relates to a printing machine, more particularly to a printing machine with a printing unit which is adapted to receive various plate cylinders.
2. Description of the Related Art
Referring to FIGS. 1 and 2, a conventional printing machine is shown to comprise a base body 11, paper pulling mechanisms 131,132 mounted at two opposed end portions of the base body 11, and a plurality of printing units 2 mounted on the base body 11 for printing a continuous paper 12 which is pulled by the mechanism 131.
Each of the printing units 2 has a pair of spaced and opposed walls 20 provided on two sides of a paper-supplying route which passes through the printing unit 2, and a plate cylinder 21 and an impression cylinder 23 which are journalled respectively between the opposed walls 20 in a parallel manner for performing a printing action. A printing plate 22 is attached to the plate cylinder 21. An inking apparatus 24 for supplying printing ink to the printing plate 22 is mounted above the plate cylinder 21 and is associated with the same.
Note that in order to make the best use of a continuous sheet of printing paper, the printing plate 22 must possess a transverse length which is equal to the circumference of the plate cylinder 21. In the event that the transverse length of the printing plate 22 is shorter than the circumference of the plate cylinder 21, a blank space is formed between adjacent printed portions of the continuous paper, thereby resulting in waste of the printing paper. To overcome this drawback, the continuous paper 12 is arranged to be pulled by the mechanism 131 so as to pass between the plate cylinder 21 and the impression cylinder 23 and in order to receive a full print from the printing plate 22 and is then retracted rearwardly from the traveling route thereof by another mechanism 132 to permit printing at the blank space thereof. Thus, the continuous paper 12 is printed with minimum waste. However, such type of forward-and-retract paper supplying system slows down the printing speed of the printing machine. Therefore, the transverse length of the printing plate 22 must be equivalent to the diameter of the plate cylinder 21 to ensure that the printing machine performs at a continuous pace with minimum waste. However, since the transverse length of the printing plate 22 varies according to the printing requirements, the diameter of the plate cylinder 21 must also be varied to ensure that the printing machine is able to make the most effective use of the continuous sheet 12 of paper. It is noted that, in the conventional printing machine, the mounting positions for the plate cylinder 21, the impression cylinder 23 and the inking apparatus 24 are formed on the opposed walls 20 at fixed positions. Thus, if the plate cylinder 21 is replaced by one with a different diameter, the replaced plate cylinder is unable to correspond with the inking apparatus 24 and the impression cylinder 23.
Accordingly, the positions of any two among the plate cylinder 21, the impression cylinder 23 and the inking apparatus 24 should be changeable to correspond with the replaced plate cylinder.